Composite prosthesis with external polymeric support structure and methods of manufacturing the same

ABSTRACT

A prosthesis including a support structure for enhancing kink and/or crush resistance. The support structure is connected to an outer surface of the prosthesis and includes at least two components, one of which has a lower melting point than the other. The component with the lower melting point is used to connect the support structure to the outer surface of the prosthesis.

RELATED APPLICATIONS

This is a divisional application of and, pursuant to 35 U.S.C. § 120,claims the benefit of priority to U.S. patent application Ser. No.14/252,710, filed on Apr. 14, 2014 (now U.S. Pat. No. 9,375,326 B2),which is a divisional application of U.S. patent application Ser. No.12/784,393, filed on May 20, 2010 (now U.S. Pat. No. 8,696,738), whereinthe entire discloses of these documents are herein incorporated byreference.

FIELD OF THE INVENTION

The present invention relates generally to an implantable device. Moreparticularly, the present invention relates to a prosthesis, such as agraft, including a support structure providing, e.g., enhanced kinkand/or crush resistance.

BACKGROUND OF THE INVENTION

Implantable devices are commonly used in medical applications. One ofthe more common device structures includes tubular prostheses, which maybe used as vascular grafts to replace or repair damaged or diseasedblood vessels. To maximize the effectiveness of such a prosthesis, itshould be designed with characteristics which closely resemble that ofthe natural body lumen which it is repairing or replacing.

One form of a conventional tubular prosthesis specifically used forvascular grafts includes a textile tubular structure formed by weaving,knitting or braiding synthetic fibers into a tubular configuration.Tubular textile structures have the advantage of being naturally porous,which allows desired tissue ingrowth and assimilation into the body.This porosity, which allows for ingrowth of surrounding tissue, must bebalanced with fluid tightness so as to minimize leakage during theinitial implantation stage. Other tubular prosthesis are formed ofexpanded polytetrafluoroethylene (ePTFE), which may be used for smallerdiameter prosthesis.

Composite ePTFE textile grafts are also known. For example, U.S. PatentPublication No. 2003/0139806 describes an inner layer of ePTFE and anouter layer of textile material bonded together by an elastomericbonding agent to form a vascular prosthesis.

It is known to provide enhanced kink and crush resistance properties toePTFE grafts by directly attaching a spirally wrapped polymeric coil orsupport element made of PTFE. The ePTFE graft is heated to a temperaturesufficient to assure that the PTFE coil bonds to the graft outersurface. This method, however, does not necessarily work well forcomposite grafts where the material of the wrapped support structure ismade from a substantially different material from the underlying graftmaterial. For example, when the underlying graft has a textile surface,attempting to attach a wrapped PTFE support member through conventionalmelting methods would likely weaken the textile layer because themelting temperature of PTFE (327° C.) is substantially higher than themelting temperature range of conventional implantable textiles, such asDacron® (polyethylenetherephthalate, 240-258° C.). This holds true forother externally wrapped support structures, which have a meltingtemperature range above that of the underlying graft body.

Joining of very different materials to form an integrated assembly hasmany challenges associated with the physical and chemical differences ofthe materials. For example, in some instances, a wrapped supportstructure is intended to be attached in a manner which prevents it frombeing removed without damaging the underlying graft. In other cases, awrapped support structure must be attached in a manner sufficient toperform its kink and crush resistance role, but allow for removalwithout damaging the underlying graft body. Such a removable supportstructure would allow the physician to tailor the graft to the patient,without risk of loss of structural integrity of the overall graftstructure. Differences in such inherent properties as meltingtemperatures, surface properties, molecular weights, biocompatibility,flexibility, solubility, as well as elongation moduli, are some of thecontributing factors which make it difficult to join dissimilarpolymeric structures together to make an implantable prosthesis havingcrush and kink resistance.

Therefore, there is a need for a composite graft that can be securablyattached to a coil or other external support element withoutcompromising the graft, and which overcomes the difficulties associatedwith joining dissimilar materials.

SUMMARY OF THE INVENTION

An example embodiment of the present invention provides an implantableprosthesis which includes: (a) a generally tubular body including anouter textile surface; and (b) a support structure attached to the outertextile surface of the body and configured to increase at least one ofthe kink and crush resistance of the body. The support structureincludes a first component and a second component. The second component(i) including a polymeric material, (ii) having a lower meltingtemperature than that of the first component and the body, and (iii)connecting the first component to the body.

According to an example embodiment, the body of the implantableprosthesis may include an inner layer made from a biocompatible polymer.

According to an example embodiment, the outer textile surface mayinclude the outer surface of an outer textile layer including filamentsor yarns with interstices or pores between them. The second componentextends into the interstices or pores and thereby mechanically connectsthe first component of the support structure to the outer textile layer.

According to an example embodiment, the outer textile layer includes aknit, weave or braid pattern of the filaments or yarns and wherein thesecond component of the support structure is removably connected to theouter textile layer such that removal of the first component does notsubstantially damage the pattern. The textile pattern of the inventionmay be chosen from any useful pattern, including but not limited toknits, weaves, braids, or other spun fiber constructions.

According to an example embodiment, the support structure may beconfigured such that removal of the first component from the outertextile layer removes a portion of the second component while leaving aremainder of the second component connected to the outer textile layer.

According to an example embodiment, a biocompatible elastomeric bondingagent bonds an outer surface of the inner layer to an inner surface ofthe outer textile layer.

According to an example embodiment, the first component has a meltingtemperature of approximately 130° C.-170° C. and the second componenthas a melting temperature of approximately 60° C.-105° C.

According to an example embodiment, the first component is made frompolypropylene.

According to an example embodiment, the second component is made frompolyethylene.

According to an example embodiment, the support structure is wrappedabout the outer textile surface. Various forms of wrapping may be used,including helical wrapping.

According to an example embodiment, the inner layer is made from atleast one of ePTFE, polyurethane, silicone, and an acrylate.Combinations of biocompatible polymers may also be used.

According to an example embodiment, the inner layer is made from ePTFE.

According to an example embodiment, the second component is disposedabout the first component. Desirably, the first component is a corecomponent and the second component is a layer or sheath that partiallyor completely covers the core.

According to an example embodiment, there is provided an implantableprosthesis which includes: (a) a generally tubular body which includesan inner biocompatible layer (referred to as a luminal orblood-contacting layer), and an outer textile layer disposed about theinner biocompatible layer; and (b) a support structure attached to theouter textile layer and configured to increase at least one of the kinkand crush resistance of the body, the support structure including a beador coil having a core component and an outer sheath componentsurrounding the core component, the outer sheath component being apolymer having a melting temperature lower than the melting temperatureof the core component and lower than the melting temperature of thebody. Desirably, the core component is also a polymer component. Thesupport structure may be formed by coating the core component with thesheath component or by co-extrusion techniques.

A method of preparing an implantable prosthesis according to an exampleembodiment of the present invention includes: (a) applying a supportstructure to an outer textile surface of a generally tubular body of theprosthesis, the support structure including a first component and asecond component disposed about the first component, the secondcomponent being polymeric and having a lower melting temperature thanthat of the first component and the body; and (b) melting the secondcomponent, and not the first component or the body, so as to cause thesecond component to connect the first component to the body.

According to an example embodiment, the method further includes thepreliminary steps of forming the body by disposing a textile outer layerover a biocompatible polymeric inner layer and connecting the outer andinner layers using a biocompatible elastomeric bonding agent.

A method of implanting a prosthesis into a subject according to anexample embodiment of the present invention includes the steps of: (a)determining an appropriate size of the prosthesis for the subject, theprosthesis including a generally tubular body and a support structureattached to an outer surface of the body and configured to increase atleast one of the kink and crush resistance of the body, the supportstructure including a first component and a second component, the secondcomponent having a lower melting temperature than that of the firstcomponent and the body, the second component connecting the firstcomponent to the body; (b) removing the first component from at leastone end of the prosthesis consistent with the appropriate size whileleaving the support structure connected along a remainder of the body;and (c) implanting the prosthesis in the subject.

Combinations of any of the aforementioned example embodiments areincluded as part of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prosthesis according to an exampleembodiment of the present invention shown in partial cross section.

FIG. 2 is a side view of the prosthesis of FIG. 1.

FIG. 3 is a cross-sectional view of the support structure of FIG. 1.

FIG. 4 is a side view of the prosthesis of FIG. 1 with the supportstructure and outer textile layer shown in cross section.

FIG. 5 is a schematic representation of an example of a mechanism usedto assemble the prosthesis of FIG. 1.

FIG. 6 is a side view and partial cross section of an example embodimentof the present invention.

FIG. 7 is a side view and partial cross section of an example embodimentof the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a prosthesis 10 according to an example embodiment of thepresent invention. The prosthesis 10 may be generally tubular, andincludes a composite implantable prosthesis having an inner layer 14,e.g., a tube made from a biocompatible polymer, and an outer layer 12,e.g., a tubular textile layer, at least partially disposed about theinner layer 14. The prosthesis 10 may have any desired thickness, e.g.,0.1 mm to about 2 mm, the thickness being measured from the outersurface of the device to the inner surface.

As detailed further below, the two layers 12, 14 may be joined, e.g.,using a bonding agent, and supported by a support structure 22. Thesupport structure 22 includes a first material and a second materialdisposed on the first material and having a lower melting point than thefirst material. This novel support structure allows the graft to beheated to a temperature sufficient to assure bonding of the supportstructure to the graft without compromising the graft.

Composite Prosthesis

Inner layer 14 may be made from of a biocompatible material, such as abiocompatible polymer, e.g., ePTFE, polyurethane, acrylates, siliconesand copolymers and combinations thereof. In one embodiment, the innerlayer 14 is made from at least one of ePTFE, polyurethane, silicone, andan acrylate.

Outer textile layer 12 may be formed from a biocompatible materialhaving at least one different property than inner layer 14. For example,outer textile layer 12 may be a textile formed from yarns that may beflat, shaped, twisted, textured, pre-shrunk or un-shrunk. The yarns maybe natural or synthetic, e.g., thermoplastic materials including, butnot limited to, polyesters, polypropylenes, polyethylenes,polyurethanes, polynaphthalenes, polytetrafluoroethylenes, expandedpolytetrafluoroethylene, and the like. The yarns may be of themultifilament, monofilament or spun types. Multifilament yarns offerincreased flexibility. Monofilament yarns are useful for enhanced crushresistance.

As used herein, the term “PTFE” refers to polytetrafluoroethylene, andrefers to any structure made at least partially ofpolytetrafluoroethylene. The term “ePTFE” refers to expandedpolytetrafluoroethylene, and refers to any structure made at leastpartially of expanded polytetrafluoroethylene.

The inner layer 14 may be produced from the expansion of PTFE formed,e.g., in a paste extrusion process. The PTFE extrusion may be expandedand sintered in a manner well known in the art to form ePTFE having amicroporous structure defined by nodes interconnected by elongatefibrils. The distance between the nodes, referred to as the internodaldistance (IND), may be varied by the parameters employed during theexpansion and sintering process. The resulting process of expansion andsintering yields pores within the structure of the inner layer 14. Thesize of the pores are defined by the IND of the inner layer 14.

The outer textile layer 12 may be designed as a tissue contactingsurface in order to promote enhanced cellular ingrowth, which maycontribute to the long term patency of the prosthesis. The inner layer14 may be used as a blood contacting surface so as to minimize leakageand to provide a generally anti-thrombogetic surface. In certainsituations, the layers may be reversed where indicated.

The inner layer 14 and the outer textile layer 12 may be bonded to eachother, e.g., using a bonding agent 20. The bonding agent may be appliedas a solution to an outer surface of the inner layer 14 or to an innersurface of the outer textile layer 12 by a spray coating process.However, other known processes may be employed to apply the bondingagent 20.

The bonding agent 20 may include, for example, various biocompatible,elastomeric bonding agents such as urethanes, polycarbonate urethanes,styrene/isobutylene/styrene block copolymers (SIBS), silicones, andcombinations thereof. Other similar materials are contemplated. Mostdesirably, the bonding agent may include polycarbonate urethanes soldunder the trade name CORETHANE® by Boston Scientific Corporation,Natick, Mass. This urethane is provided as an adhesive solution withpreferably 7.5% Corethane, 2.5 W30, in dimethylacetamide (DMAc) solvent.

For inner layers 14 made from ePTFE, a highly hydrophobic material, itis useful to use a elastomeric bonding agent 20, which makes it way intothe micropores of the ePFTE structure, enhanced bonding. One example ofa class of bonding agent with elastic properties are those formed fromthe reaction of alphatic macroglycols and aromatic or aliphaticdiisocyanates.

Monofilament Biocompatible Polymeric Support Structure

With reference to FIGS. 2-4, the prosthesis 10 is wrapped with a supportstructure 22 in order to enhance crush and/or kink resistance. Thesupport structure 22 may extend along the entire length of theprosthesis 10 or just along select portions, e.g., those requiringadditional support. The support structure 22 may be produced separatelyfrom the prosthesis layers, e.g., by casting or extrusion.

The support structure 22 may include materials having different meltingtemperatures. As illustrated, support structure 22 has a first component23 at least partially surrounded by a second component 24 which has alower melting point than that of the first component 23. The secondcomponent 24 is at least partially disposed about the first component24. The first component 23 and second component 24 may be coextruded.The second component 24 need not entirely surround the first component23 prior to connection to the body 10 so long as second component 24,upon melting and subsequently cooling, extends through interstices orpores in the outer textile layer 12 of the prosthesis 10 and also wrapsaround the first component 23 sufficient to create a hold on the firstcomponent 23. The support structure 22 may have a core first component23 surrounded by a sheath second component 24.

The second component 24 is made from a material, desirably a polymericmaterial, having a lower melting point than the first component 23. Forexample, the second component 24 may include a polyethylene polymer, andthe first component 23 may include a polypropylene polymer. This permitsthe prosthesis 10 to be heated to a melting temperature high enough tomelt the second component 24 of the support structure 22, such that itmay flow into interstices or pores of the textile layer 12 of theprosthesis 10, but not high enough to melt the first component 23 of thesupport structure 22 or the inner layer 14 and outer textile layer 12 ofthe prosthesis 10. Thus, the second component 24 connects the firstcomponent 23 to the prosthesis 10.

The support structure 22 may have any cross-sectional configuration. Thecross section of the support structure 22 may be selected so as tomaximize the surface area through which it may be fused to the outertextile layer 12 of the prosthesis 10. The cross section of the supportstructure 22 may also be selected, e.g., a semicircle or half moon, soas to, minimize the external irregularity or roughness of the prosthesis10 by limiting the height of the support 22 above the outer textilelayer 12.

The overall size and geometry of the support structure 22 are adaptabledepending on the material used and the desired end properties of theprosthesis 10.

The support structure 22 may be attached to the outer textile layer 12such that it is removable or non-removable, as further discussed herein.In one embodiment, the physician can remove or unravel the supportstructure 22 from the outer textile layer 12 in order to size or tailorthe prosthesis 10 to the patient.

In another embodiment, the support structure 22 may be heated at atemperature, e.g., above 160° C., sufficient to cause both the firstcomponent 23 (i.e., the core) and the second component 24 (i.e., thesheath) to melt. If the polymeric support structure is not adequatelydisposed about or wrapped around the prosthesis, then it will simplymelt off the surface of the prosthesis. However, if the polymericsupport structure is contained during the melting process, then bothpolymers will flow into the outer textile layer 12 of the prosthesis 10and flatten-down, or in some cases be recessed, to achieve a low profileallowing, e.g., for the use of a smaller diameter delivery mechanism. Insome embodiments, the total profile will essentially be the same as oronly nominally above the profile of the underlying prosthesis 10.

In another embodiment, the support structure 22 may be applied to only asection of the base of the prosthesis 10, for example, leaving the endseither unsupported or supported with a removable polymeric support tocreate a prosthesis that is customizable. The customizable ends willallow the physician to cut the prosthesis 10 to the appropriate lengthand still make the necessary sutures for implantation.

In an example embodiment, the first component 23, e.g., made frompolypropylene, has a melting point which is about 130° C.-170° C. andthe second component 24, e.g., made from polyethylene, has a meltingpoint of about is 60° C.-105° C.

As shown in FIG. 2, prosthesis 10 has a polymeric support structure 22wrapped helically around the prosthesis 10 and connected thereto. Thepolymeric support structure 22 of the prosthesis 10 as shown is amonofilament, but may be a braid of two or more, e.g., smaller,filaments. Alternatively, the polymeric support structure may becomposed of two or more filaments wrapped independently about the outertextile layer 12. Each filament may be composed of a single monofilamentor may be composed of an arrangement of two or more filaments mutuallyintertwined, e.g., in a regular braid or twist pattern.

The support structure 22 may be comprised of a single filament lengthwrapped helically around the tube for the length of the outer textilelayer 12. Alternatively, one or more support structures may extendlongitudinally along a length of the prosthesis 10. Further, thefilament component may be discontinuous, being comprised of more thanone segment of filament wrapped or otherwise arranged along the outertextile layer 12. If more than one segment is employed, the segments maybe wrapped sequentially, so that the ends of each segment are juxtaposedwith each adjacent segment end and attaching each segment to the outertextile layer 12 so that segment ends are as close to each other in thelongitudinal dimension as possible. Arrangements in which such segmentsare not matched in helical and/or longitudinal position are alsocontemplated as an embodiment of the invention. Alternatively, when morethan one filament segment is used, the segments may overlaplongitudinally such that two or more segments, whether of identical ornon-identical lengths and/or diameters, may be fused to the outertextile layer 12 at any plane along the length of the prosthesis 10.

In an example embodiment, the support structure 22 may be wrapped aroundthe outer textile layer 12, e.g., at an angle of winding, relative tothe axis, of from about 30° to about less than 90°.

In an example embodiment with more than one support structure wrappedabout the outer textile layer 12, the angle of winding of each thesupport structures 22 may be equal to that of the others so that thesupport structures 22 are substantially mutually parallel, i.e.,non-overlapping.

In another embodiment, the support structure 22 may be wrapped undertension against the outer textile layer 12 of the prosthesis 10 and maybe heated to a temperature sufficient to melt the second component 24 ofthe support structure 22. The heating is conducted such that the secondcomponent 24 flows into and removably adheres to the outer textile layer12 of the prosthesis 10 while also remaining sufficiently disposed aboutfirst component 23. Second component 24 cools on first component 23 andis configured about first component 23 in a manner allowing it tophysically hold onto first component 23 and resist up to a predeterminedlevel of pulling force separating first component 23 from outer textilelayer 12, e.g., 10 grams to 300 grams. The connection between the secondcomponent 24 of the support structure 22 and the outer textile layer 12of the prosthesis 10 is strong enough to withstand such predeterminedpulling force and remains intact, thus preserving the integrity of theouter textile layer 12 of the prosthesis 10, even upon removal of firstcomponent 23 from the prosthesis 10 (although removal of the firstcomponent 23 may take a portion of the second component 24 of thesupport structure 22 with it). After heating, a removable supportstructure 22 is created. This permits the physician with the option ofcustomizing the supported length to suit his/her needs and provide anarea that is capable of being sutured.

In another embodiment, the support structure 22 may be wrapped undertension against the outer textile layer 12, and may be heated to atemperature to melt both the first component 23 and the second component24 and compressed against the second component 24 of the prosthesis 10to effectuate a non-removable adherence to the prosthesis 10. Afterheating, a low profile non-removable support is created.

In another embodiment, if the ends of the prosthesis 10 are completelyunsupported or supported with a removable polymeric support material, itwill create a prosthesis with a support structure that is customizable.The customizable ends will allow the physician to cut the prosthesis 10to the appropriate length and still be able to make the necessarysutures.

The support structure 22 may be wrapped around the outer textile layer12 while under tension, otherwise the support structure 22 might slipand/or be displaced during manipulation prior to sintering. The tensionlevel is sufficient to avoid slippage while low enough to avoid damageto the support structure 22. The compression may be applied by aflexible tubular wrap or sheath. The flexible tubular wrap or sheath maybe a shrink wrap silicone, or a textile wrap designed to tightly fitabout the structure.

In one embodiment, the support structure 22 may be melted to the tubularouter textile layer 12 of the prosthesis. This allows the formation of asupport structure 22 integrated with the prosthesis 10 without requiringadditional means for causing the tubing and the polymeric supportcomponents to adhere to one another. The outer textile layer 12 may bemade from a textile, e.g., woven or knit, including overlapping orinterconnecting filaments or yarns forming interstices between thefilament or yarns. The second component 24 of the support structure 22extends into the interstices and thereby mechanically connects the firstcomponent 23 of the support structure 22 to the outer textile layer 12.

Accordingly, adhesives, laminates or other physical means formaintaining the integrity of the composite prosthesis are renderedunnecessary, thus simplifying the structure of the prosthesis 10 and themethod of its manufacture.

In another embodiment, the support structure 22 may be adhered orotherwise bonded to the prosthesis 10. The material of the secondcomponent 24 of the support structure 22 may be adapted or chosenspecifically to ensure an excellent bond with the outer textile layer 12of the prosthesis while the first component 23 may be chosen to assureideal physical support properties for the prosthesis.

In another embodiment, the support structure 22 may be melted to theouter textile layer 12 of the prosthesis 10 substantially continuouslyor discontinuously along the length of the prosthesis 10.

In an example embodiment, the support structure 22 may be in the form ofa bead and may be configured to be flat, square, or ribbon-likespherical elliptical or other shapes.

Methods of Assembly

Having described the prosthesis 10 of the present invention, an examplemethod of manufacturing the prosthesis 10 in accordance with the presentinvention may now be described.

Generally, the prosthesis 10 is formed from an inner layer 14, an outertextile layer 12 at least partially disposed about the inner layer 14and joined thereto by a bonding agent 20. A support structure 22, madeup of core material 23 and second component 24, is applied to the outertextile layer 12. The second component 24 is melted onto the outertextile layer 12 to thereby adhere the support structure 22 to theprosthesis 10. The support structure 22 may be melted, for example, byapplication of heat at a temperature sufficient to melt the secondcomponent 24 but not the first component 23 (or core) of the supportstructure 22.

The inner layer 14 of prosthesis 10 may be formed in a conventionalforming process such as by tubular extrusion or by sheet extrusion wherethe sheet is formed into a tubular configuration. The inner layer 14 isplaced over a stainless steel mandrel and the ends of the tube aresecured. The prosthesis is then spray coated with an adhesive solutionof anywhere from 1%-15% Corethane® urethane, 2.5 W30 in DMAc. As notedabove, other adhesive solutions may also be employed. The coated innerlayer 2 may be dried at room temperature. Alternatively, it may beplaced in an oven heated in a range from 18° C. to 150° C. oven for 5minutes to overnight to dry off the solution. If desired, the spraycoating and drying process can be repeated multiple times to add moreadhesive to the inner layer 14. The inner layer 14 is then covered withthe outer textile layer 12 to form the composite prosthesis 10. One ormore layers of resilient sheath, is then placed over the compositestructure to hold the composite structure together and assure thatcomplete contact and adequate pressure is maintained for bondingpurposes. The assembly of the composite prosthesis within the sheath isplaced in an oven and heated in a range of 180°-220° C. forapproximately 5-30 minutes to bond the layers together.

One technique used to attach the support structure 22 to the outertextile layer 12 is shown in FIG. 4. In this example, prosthesis 10 is agraft composed of multiple layers including textile and ePTFE and hasjoined thereto, e.g., in a helical fashion therearound, a two-layersupport structure 22. In order to join the support structure 22 to theprosthesis 10, the prosthesis 10 is placed over a solid mandrel 15.Conventional external heating, e.g., by a convection oven, (arrows A),is applied to the support structure 22 positioned over the prosthesis10. While this is adequate to bond the support structure 22 to the outerlayer 12, heating in this manner may cause the second component 24 ofthe support structure to uncontrollably flow and create fillets 13 atthe juncture of the support structure 22 and the outer textile layer 12of the prosthesis 10 thereby forming a tent configuration between theouter textile layer 12 and the support structure 22. This method ofattachment via conventional external heating, as indicated by arrows A,results in a reduced peel strength of attachment that is undesirable andfurther causes an area of reduced flexibility due to the larger andthicker fillet areas formed by the melted polymer. While compositeprostheses of the present invention formed in this manner results in ahigher degree of crushed and kink resistance, the composite structuremay lose flexibility which is desirable in an implantable prosthesis.Also, as noted there may be a tendency for the support structure to losecertain of its peel strength of attachment.

Referring now to FIG. 5, another technique for connecting the supportstructure 22 to the prosthesis 10 is described. The prosthesis 10 havingsupport structure 22, e.g., coiled therearound, is placed on a mandrel30, e.g., made from 316 stainless steel tubing. The mandrel 30 is heatedfrom within the prosthesis 10 to effectuate melting of the supportstructure 22 to the prosthesis 10. The heat is transferred in thedirection of arrows B from the mandrel 30 to the prosthesis 10. Themandrel may be heated in a wide variety of manners. The mandrel may beheated by applying heated fluids, such as liquid or high temperaturegranular solids such that the composite prosthesis is melted by raisingthe temperature of the support structure 22 above its melting point.

In accordance with one embodiment of the present invention, a heatedcirculating bath 32 of, e.g., fluid or granular solids, is heated toapproximately above the melting point of at least the second region 24of the support structure 22, e.g., above about 60-105° C. A pump (notshown) circulates the heated material through the mandrel 30. The heatfrom the material passing through the mandrel 30 is transferred throughthe wall of the mandrel (arrow B) and into the surface of the outertextile layer 12 of the prosthesis 10 sufficient to melt at least thesecond component 24 of the support surface 22.

A pump (not shown) in the heater bath 32 circulates the heated materialthrough the mandrel 30 and back into the bath 32. The heat from thematerial passing through the mandrel 30 is transferred through a wall ofthe mandrel and through the prosthesis. The prosthesis is held in thisstate for enough time to melt just the second component 24, e.g., madefrom polyethylene, of the support structure 22 in contact with the outertextile layer 12 of the prosthesis, e.g., made from ePTFE.

Attachment of the support structure 22 may also be effectuated byapplying pressure, with or without heat, to compress the supportstructure 22 against the outer textile layer 12 to produce a low profilestructure. The pressure may be applied, e.g., using a flexible wrappersheath. The flexible wrapper sheath may be formed, e.g., from a textileor polymer.

It is also contemplated that the present technique could be used to coolproducts which require low temperature cycle. Alternatively, afterheating the composite prosthesis the mandrel can be used to inject lowtemperature fluid into the line to rapidly cool the product. Temperaturecontrol or changes may be used to temper or anneal products to createvarious polymer microstructures for various performance criteria.

The attachment process described in FIG. 5 may also be used withdifferent support structures, for example, those made from a singlematerial or multiple materials and wrapped in different configurationsas well.

Use of a support structure 22 having a first component 23 with a meltingpoint greater than the melting point of the second component 24 allowsthe appropriate amount of heat to be applied so that only the secondcomponent 24 melts, i.e., the heat applied is above the melting point ofthe second component 24, but lower than the melting point of the firstcomponent 23. The result of such melting is shown in FIG. 6. As can beseen, heat applied from within the prosthesis 10 effectuates melting ofthe outer layer material 24 such that it cools on the bottom of theinner layer material 23, i.e., where the support structure 22 contactsthe outer textile layer 12 of the prosthesis, and may partially resideor soak into the outer textile layer 12, e.g., extending intointerstices in the knit or woven structure of the outer textile layer12, serving to connect the first component 23 to the prosthesis 10. Theconnection is strong enough to keep the support structure in place alongthe prosthesis 10 during use in a patient's body but also allows thesupport structure 22 to safely be pulled off the outer textile layer 12,e.g., along the ends of the prosthesis 10 so as to allow sizing beforeimplantation, without substantial damage to the, e.g., knit or wovenpattern, of the outer textile layer 12. The connection may be configuredsuch that removal of the first component 23 from the outer textile layer12 removes a portion of the second component 24, while leaving aremainder of the second component 24 connected to the outer textilelayer 12.

According to another example method for making the prosthesis 10, theend product of which is shown in FIG. 7, melting is performed at atemperature above the melting point of both the first component 23 andthe second component 24. In such an embodiment, the entire supportstructure 22 is at least partially melted and allowed to soak into andbond to the outer textile layer 12, which provides for a non-removablelower profile support structure.

According to another example method for making the prosthesis 10, thistime a composite prosthesis structure having a ePTFE inner layer and atextile outer layer, the prosthesis is placed on a stainless steelmandrel and has a barium sulfate-containing polypropylene/polyethylenebicomponent monofilament support structure wrapped about it undertension. The barium sulfate is a radiopaque material and allows forvisualization under fluoroscopy by the physician.

This sub-assembly is placed in a laboratory convection oven at 140° C.for 8 minutes. After the oven cycle, and once the prosthesis is cool, itcan be removed from the mandrel. The result is a prosthesis with atraditional bead support structure that is radiopaque and removable tocustomize.

According to another example method of making prosthesis 10, theprosthesis 10 is covered by a silicone tube, a layer of knit material, asecond layer of silicone tube, and a PTFE tape wrap. Thesilicone-knit-silicone-PTFE covering is used to apply pressure to theprosthesis during the heating cycle. After heating the prosthesis at170° C. for 8 minutes in a laboratory convection oven, thesilicone-knit-silicone-PTFE covering is removed and discarded. Theresult is a prosthesis with a low profile, non-removable, radiopaque,support wrap that is melted into the outer layer of the prosthesis.

According to another embodiment of the invention, there is provided amethod of implanting a prosthesis 10 into a subject according to anexample embodiment of the present invention. The method includes thesteps of: (a) determining an appropriate size of the prosthesis 10 for asubject, the prosthesis 10 including a generally tubular body and asupport structure 22 attached to an outer surface of the body andconfigured to increase at least one of the kink and crush resistance ofthe body, the support structure 22 including a first component 23 and asecond component 24, the second component 24 having a lower meltingtemperature than that of the first component 23 and the body, the secondcomponent 24 connecting the first component 23 to the body; (b) removingthe first component 23 from at least one end of the prosthesis 10consistent with the appropriate size while leaving the support structure22 connected along a remainder of the body; and (c) implanting theprosthesis 10 in the subject.

Various changes to the foregoing described and shown structures wouldnow be evident to those skilled in the art. Accordingly, theparticularly disclosed scope of the invention is set forth in thefollowing claims.

What is claimed is:
 1. An implantable prosthesis comprising: (a) agenerally tubular body comprising an outer textile surface; and (b) asupport structure attached to the outer textile surface of the tubularbody and configured to increase at least one of kink resistance andcrush resistance of the tubular body, wherein the support structurecomprises a first component made from polypropylene and a secondcomponent, wherein the first component has a melting temperature of 130°C.-170° C., wherein the second component comprises a polymeric materialmade from polyethylene so the second component has a melting temperatureof 60° C.-105° C. that is a lower melting temperature than that of thefirst component and the body, and the second component connects thefirst component to the tubular body, and wherein a portion of the firstcomponent and a portion of the second component are removable withrespect to the outer textile surface without substantially compromisingthe outer textile surface of the tubular body.
 2. The implantableprosthesis of claim 1, wherein the tubular body of the implantableprosthesis comprises an inner layer made from a biocompatible polymercomprising ePTFE.
 3. The implantable prosthesis of claim 1, wherein theouter textile surface is an outer surface of an outer textile layercomprising filaments or yarns with interstices or pores between thefilaments or yarns, wherein the second component extends into theinterstices or pores and thereby mechanically connects the firstcomponent of the support structure to the outer textile layer.
 4. Theimplantable prosthesis of claim 3, wherein a biocompatible elastomericbonding agent comprising polycarbonate urethane bonds an inner layerouter surface to an inner surface of the outer textile layer.
 5. Theimplantable prosthesis of claim 3, wherein a connection between thesupport structure and the tubular body is sufficiently strong to securethe support structure to the outer textile surface when the prosthesisis positioned in a patient's body but also allows a portion of thesupport structure to be safely pulled off the outer textile surface soas to allow for sizing of the prosthesis.
 6. The implantable prosthesisof claim 1, wherein the outer textile layer comprises a knit, woven orbraid pattern of filaments or yarns and wherein the second component ofthe support structure is removably connected to the outer textile layersuch that removal of the second component does not substantially damagethe knit or woven pattern.
 7. The implantable prosthesis of claim 6,wherein a portion of the support structure is configured to be removablyattached to the outer textile layer such that removal of the portion ofthe first component relative to the outer textile surface removes theportion of the second component while leaving a remainder of the secondcomponent connected to the outer textile surface.
 8. The implantableprosthesis of claim 6, wherein a biocompatible elastomeric bonding agentcomprising polycarbonate urethane bonds an inner layer outer surface toan inner surface of the outer textile layer.
 9. The implantableprosthesis of claim 1, wherein the second component is disposed aboutthe first component so as to physically hold onto the first component soas to resist a pulling force up to 10 grams to 300 grams.
 10. Theimplantable prosthesis of claim 1, wherein the support structure has asemicircle cross-section or a half moon cross-section.
 11. Theimplantable prosthesis of claim 1, wherein the support structure isapplied to the body such that the support structure is helically wrappedaround the body.
 12. A method of preparing the implantable prosthesisaccording to claim 1, wherein the method comprises the steps of: (a)applying the support structure to the outer textile surface of thetubular body of the prosthesis so as to create a connection between thesupport structure and the tubular body sufficiently strong so as tosecure the support structure to the outer textile surface and withstanda predetermined pulling force but also allows a portion of the supportstructure to be detachable with respect to the outer textile surface soas to be capable of being safely pulled off along a length of the outertextile surface to facilitate sizing the prosthesis; and (b) melting thesecond component so as to cause the second component to connect thefirst component to the tubular body so as to physically hold onto thefirst component so as to resist a pulling force up to 10 grams to 300grams, wherein the second component is melted at a temperature between60° C. and 105° C.
 13. The method of claim 12, further comprising thepreliminary steps of forming the tubular body by disposing a textileouter layer over a biocompatible polymeric inner layer comprising ePTFEand connecting the outer and inner layers using a biocompatibleelastomeric bonding agent formed from the reaction of aliphaticmacroglycols and aromatic or aliphatic diisocyanates.
 14. The method ofclaim 12, further comprising the steps of determining an appropriatesize of the prosthesis for implantation into a subject and removing thefirst component from at least one end of the prosthesis consistent withthe appropriate size while leaving the support structure connected alonga remainder of the tubular body without substantially damaging the outertextile surface.
 15. The method of claim 12, further comprising the stepof: melting the second component so as to cause the second component toextend into the tubular body.
 16. The method of claim 12, wherein thefirst component is not melted during the melting of the secondcomponent.